.background-box1 {
  position: absolute;
  left: 5px;
  right: 5px;
  top: 5px;
  bottom: 5px;
  border: 1px solid rgba(191, 191, 191, 1);
  box-shadow: 0 0 5px rgba(191, 191, 191, 1);
  z-index: 0;
}
.background-box2 {
  position: absolute;
  left: 7px;
  right: 7px;
  top: 5px;
  bottom: 5px;
  border: 1px solid rgba(191, 191, 191, 1);
  box-shadow: 0 0 5px rgba(191, 191, 191, 1);
  z-index: 1;
}
.background-box3 {
  position: absolute;
  left: 9px;
  right: 9px;
  top: 5px;
  bottom: 5px;
  border: 1px solid rgba(191, 191, 191, 1);
  box-shadow: 0 0 5px rgba(191, 191, 191, 1);
  z-index: 2;
  /* display: flex;
  justify-content: space-between;
  place-content: center; */
  overflow: hidden;
}
/* 控制小于888px是书脊消失 */
@media screen and (max-width: 888px) {
  .background-box3 {
    display: none;
  }
}
.book-spine {
  position: absolute;
  width: 1px;
  height: 100%;
  position: absolute;
  left: 50%;
  /* bottom: 100%; */
  bottom: 0;
  border: 2px solid rgba(191, 191, 191, 1);
  border-left: none;
  box-sizing: border-box;
  z-index: 15;
}

.spine-shadow-left {
  width: 68px;
  height: 100%;
  background: url("../../assets/gradient-left.png") repeat-y;
  z-index: 10;
  margin: 0;
  z-index: 10;
  position: absolute;
  left: calc(50% - 68px);
}

.spine-shadow-right {
  width: 68px;
  height: 100%;
  background: url("../../assets/gradient-right.png") repeat-y;
  z-index: 10;
  margin: 0;
  box-sizing: border-box;
  position: absolute;
  right: calc(50% - 68px);
}
